This project is designed to prepare a GMP quality investigational HIV vaccine and complete the preclinical and laboratory studies needed to begin a clinical trial. The Vaccine Research Center (VRC), NIAID is developing a novel prime-boost HIV vaccine strategy directed at the three most globally prevalent HIV subtypes (clades). VRC's HIV prime-boost candidate is designed to elicit immune responses to HIV sequences from clades A, B and C which together cause about 90 percent of incident HIV infections around the world. In November 2002, the VRC Clinical Trials Core launched a Phase I clinical study (VRC 004) of a multiclade, multigene DNA vaccine at the NIH Clinical Center (Bethesda, MD) as the first step in developing the prime-boost regimen.